Novel glass ionomer cements for biomedical applications.

Since their invention in the late 1960's, glass ionomer cements (GICs) have been used extensively in dentistry but recently they have also been utilised as bone cements in ear nose and throat (ENT) surgery. Unfortunately, AI3+, a component of conventional ionomer glasses, has been linked to poor bone mineralisation and neurotoxicity. Consequently, the aim of the research was to modify the glass composition in GIC bone cements to reduce the amount of AI3+ present and therefore its potential release during clinical usage. Fe2O3 was therefore substituted for AI2O3 in the glass formulations and the resulting cements compared with conventional GIC's
Glasses with molar compositions of 4.5SiO2∙XM2O3∙YP2O5∙3CaO∙2CaF2 (M = AI or Fe, X = 3 or 1.5 Y = 0 – 1.5)were fabricated using a conventional glass-processing route. Cements were prepared using a standard ratio; 1 g of glass powder: 0.2 g of dried polyacrylic acid: 0.3 g of 10% tartaric acid solution, and their setting times, mechanical properties, and in-vitro biocompatibility evaluated.
AI2O3-based glasses were amorphous when cast into water but crystallised to apatite and mullite when heat treated at 750°C and 950°C, respectively. In contrast, Fe2O3-based glasses devitrified to magnetite and apatite on cooling irrespective of the quench rate. Cements could be fabricated from all glasses and glass ceramics. GIC's based on Fe2O3 containing glasses gave similar mechanical properties to conventional AI2O3 based GIC's and several compositions were identified whose setting times were appropriate for clinical usage. Good in vitro biocompatibility was observed for all Fe2O3 - based cements and for those formed from AI2O3-based ionomer glasses crystallised at 750°C to form apatite.